Chemical characterisation of a new estuarine pollutant (2,4-Dichloro-6-Nitrophenol) and assessment of the acute toxicity of its quinoid form for Artemia salina |
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Authors: | Antonio Tognazzi Arduino M Dattilo Luca Bracchini Claudio Rossi Davide Vione |
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Institution: | 1. Dip. Farmaco Chimico Tecnologico, Università degli Studi di Siena , Via Aldo Moro 2, 53100 Siena , Italy;2. CSGI (Inter-University Center for Colloid and Surface Science) , Via della Lastruccia 3, 50019 Sesto Fiorentino (FI) , Italy tognazzi@unisi.it;4. CSGI (Inter-University Center for Colloid and Surface Science) , Via della Lastruccia 3, 50019 Sesto Fiorentino (FI) , Italy;5. Dipartimento di Chimica Analitica , Università degli Studi di Torino , Via Pietro Giuria 5, 10125 Torino , Italy;6. Centro Interdipartimentale NatRisk, Università degli Studi di Torino , Via Leonardo da Vinci 44, 10095 Grugliasco (TO) , Italy |
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Abstract: | It is known that the compound 2,4-dichloro-6-nitrophenol (2,4DC6NP) is formed upon nitration of 2,4-dichlorophenol, which in turn is a transformation intermediate of the herbicide dichlorprop. However, the chemical and spectroscopic characteristics of 2,4DC6NP, as well as its toxicity, are poorly known. This work shows that 2,4DC6NP behaves as a diprotic acid in aqueous solutions, with pKa values of 3.0?±?0.9 and 4.9?±?0.5. At pH?<?3, 2,4DC6NP would undergo protonation. The absorption spectra suggest that anionic 2,4DC6NP, which prevails at pH?>?5 would have an ortho-quinoid structure that is responsible for the absorption peak centred at 428?nm. Considering that 2,4DC6NP has been detected in the brackish lagoons of the Rhône delta (southern France), where its levels are comparable to those of the parent herbicide, it is necessary to examine the possible effects of 2,4DC6NP on the species living in that environment. For this reason, the acute toxicity of the anionic form of 2,4DC6NP was assessed for the brine shrimp Artemia salina, a zooplankton species that lives both in brackish and in saline aquatic environments. The toxicity test yielded a LC20 value of 8?±?2?mg?L?1 and a LC50 value of 18.7?±?0.8?mg?L?1. Such values are safely higher than the maximum detected concentration of 2,4DC6NP in the Rhône delta lagoons. Further studies should be concentrated on the long-term effects of 2,4DC6NP, and in particular on its potential genotoxicity. |
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Keywords: | Artemia salina 2 4-dichloro-6-nitrophenol acute toxicity nitroaromatic compounds saltwater crustaceans pesticides |
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